Acts like rev limiter is in place

[tt460]

I have a newly rebuilt engine and have around 100 miles on it now. Displacement was increased by 10%, made some changes to the calibration to accommodate increase in displacement. Most everything else in the combination has stayed the same and ran very well before the rebuild. Have put enough miles on the engine to start opening it up a little, but when the engine gets to about 85kpa manifold pressure and above, it acts like it's hitting a rev limiter.

Calibration is 2bar OS running speed density. Has a positive displacement supercharger pulled for about 7#.

At one point in the log (05:50:46) Dynamic Airflow is calculating out at 1.78g, which is way off the chart for the spark table. It's at this point that it acts like it's knocking and pulling a ton of timing out. Initially I thought maybe it was blowing spark out, so I regapped plugs. All plugs look good and no signs of detonation on them. I believe it is false knock I'm seeing. Have tried to run down any potential fueling issues I could be having, but it has a really good return style fuel system. Fuel filter was changed, fuel pressure gauge says I have good pressure, fuel pressure regulator is same I had before started experiencing this. Grounds have been replaced.

Have tried added a ton of fuel to see if that fixed it and it doesn't help. Pulled timing and that hasn't helped either. Added timing when we thought it was too conservative. None of those things helped it out. Like I say in the title it acts like it's activating a rev limiter. Engine runs very well everywhere else, idles smooth, cruises nice, doesn't over heat.

Any ideas on where to begin?

20230620 Driving.hpl99 Silverado 6.6SC_Base8 No DFCO.hpt

[blindsquirrel]

It would help a TON if you'd add injector pulse widths to your channels. Also Delivered Torque.

You have non-stock injectors, but only updated the flow rate and left all the other injector tables stock?

Do you have a MAP sensor that actually uses 200/10.33 as the linear/offset, or has that just been left at the default values that get auto-populated when the custom OS is applied?

You are not in speed density, not with P0101-103 set to No MIL.

What is the engine, and what's the new bore/stroke? Why am I having to ask for this? Why does it seem like that was specifically avoided?

You should probably disable all the stuff related to the AIR pump - Disable ECT at Engine > General, and all the related DTCs.

The spark table is using cylinder airmass, not dynamic airflow.

[Alvin]

I have a newly rebuilt engine and have around 100 miles on it now. Displacement was increased by 10%, made some changes to the calibration to accommodate increase in displacement. Most everything else in the combination has stayed the same and ran very well before the rebuild. Have put enough miles on the engine to start opening it up a little, but when the engine gets to about 85kpa manifold pressure and above, it acts like it's hitting a rev limiter.

Calibration is 2bar OS running speed density. Has a positive displacement supercharger pulled for about 7#.

At one point in the log (05:50:46) Dynamic Airflow is calculating out at 1.78g, which is way off the chart for the spark table. It's at this point that it acts like it's knocking and pulling a ton of timing out. Initially I thought maybe it was blowing spark out, so I regapped plugs. All plugs look good and no signs of detonation on them. I believe it is false knock I'm seeing. Have tried to run down any potential fueling issues I could be having, but it has a really good return style fuel system. Fuel filter was changed, fuel pressure gauge says I have good pressure, fuel pressure regulator is same I had before started experiencing this. Grounds have been replaced.

Have tried added a ton of fuel to see if that fixed it and it doesn't help. Pulled timing and that hasn't helped either. Added timing when we thought it was too conservative. None of those things helped it out. Like I say in the title it acts like it's activating a rev limiter. Engine runs very well everywhere else, idles smooth, cruises nice, doesn't over heat.

Any ideas on where to begin?

20230620 Driving.hpl99 Silverado 6.6SC_Base8 No DFCO.hpt

Can you get a log where you stay in the gas a little longer?

The timing table at higher Gram/cyc /RPM is pretty weak. I'd shoot for 9 degrees aboslute minium. I think I saw -6. The point of concern with your log was 5 which is still pretty low. Too low of timing will cause issues too.

The knock retard I'm seeing isn't terrible. The max was 5.

You've double checked it has fuel pressure?

Your logging two widebands.. one is stuck at 14.66 so if any math is using AFR its going to average the real wideband reading with that one stuck at 14.66. I'd delete the extra one right away before it leaves you astray tuning.

[tt460]

You have non-stock injectors, but only updated the flow rate and left all the other injector tables stock?

Do you have a MAP sensor that actually uses 200/10.33 as the linear/offset, or has that just been left at the default values that get auto-populated when the custom OS is applied?

You are not in speed density, not with P0101-103 set to No MIL.

I purchased vehicle several years ago and the original tune I believe was built with input from Lingenfelter, so I have to assume MAP, injector tables, etc are all correct. It ran properly with no driveability issues until I had a valvetrain failure that necessitated a bottom end rebuild.

It must in speed density since there is no MAF. I'm assuming that there is something in this Custom OS that doesn't require the P0101 to be set to error.

What is the engine, and what's the new bore/stroke? Why am I having to ask for this? Why does it seem like that was specifically avoided?

6.0L LQ4, 4.010" bore x 4" stroke.

The spark table is using cylinder airmass, not dynamic airflow.

I misspoke and meant to say cylinder airmass.

I believe my issue lies in the VE table. I come from tuning non-airmass based ECUs so I think I applied too much there which is causing cylinder airmass to mis-calculate. My issue starts where the VE table starts to not make sense understanding what I know now.

[tt460]

Can you get a log where you stay in the gas a little longer?

Power fell off pretty hard when it starts to pull timing, so I've never stayed in it more than a second or two since it's clearly not happy. I wasn't sure if it was really knocking or if it was false knock (which I certain it is false knock). If I get the VE issue figured out where it runs half right I would stay in it longer.

The timing table at higher Gram/cyc /RPM is pretty weak. I'd shoot for 9 degrees aboslute minium. I think I saw -6. The point of concern with your log was 5 which is still pretty low. Too low of timing will cause issues too.

The knock retard I'm seeing isn't terrible. The max was 5.

Was starting conservative. This also only uses the low octane table since it is SD, so I've only been updating there.

You've double checked it has fuel pressure?

Has good pressure. Good return style system with multiple pumps, Kenne Bell Boost-A-Pump, and FP gauge. It's ~58 at atmospheric and rises with manifold pressure. I changed fuel filter just to be safe.

Your logging two widebands.. one is stuck at 14.66 so if any math is using AFR its going to average the real wideband reading with that one stuck at 14.66. I'd delete the extra one right away before it leaves you astray tuning.

I don't think any math uses the widebands, I'm just using them for reference. They're getting old and one has gone dead. Have just been ignoring the dead one.

[blindsquirrel]

I purchased vehicle several years ago and the original tune I believe was built with input from Lingenfelter, so I have to assume MAP, injector tables, etc are all correct. It ran properly with no driveability issues until I had a valvetrain failure that necessitated a bottom end rebuild.

It must in speed density since there is no MAF. I'm assuming that there is something in this Custom OS that doesn't require the P0101 to be set to error.



6.0L LQ4, 4.010" bore x 4" stroke.



I misspoke and meant to say cylinder airmass.

I believe my issue lies in the VE table. I come from tuning non-airmass based ECUs so I think I applied too much there which is causing cylinder airmass to mis-calculate. My issue starts where the VE table starts to not make sense understanding what I know now.

Sure, it's reasonable to assume the data is correct right up until you ask for help, post the tune, and somebody checks it for you and tells you it's not correct. If you still stick with your assumption after that you're not really asking for help.

[SiriusC1024]

Sure, it's reasonable to assume the data is correct right up until you ask for help, post the tune, and somebody checks it for you and tells you it's not correct. If you still stick with your assumption after that you're not really asking for help.

Yeah I'll add to that with this:

Was starting conservative. This also only uses the low octane table since it is SD, so I've only been updating there.

SD 2-bar OS uses both Hi and Lo tables.
https://support.hptuners.com/hc/en-u...r-Differences-

Listen to the advice. Fail the MAF. Check PN on MAP sensor to make sure it's 2-bar. Verify injector data.

[Alvin]

Power fell off pretty hard when it starts to pull timing, so I've never stayed in it more than a second or two since it's clearly not happy. I wasn't sure if it was really knocking or if it was false knock (which I certain it is false knock). If I get the VE issue figured out where it runs half right I would stay in it longer.

Has good pressure. Good return style system with multiple pumps, Kenne Bell Boost-A-Pump, and FP gauge. It's ~58 at atmospheric and rises with manifold pressure. I changed fuel filter just to be safe.

I don't think any math uses the widebands, I'm just using them for reference. They're getting old and one has gone dead. Have just been ignoring the dead one.

You might just need to stay in it long enough so we can see what is going on.

As long as your watching fuel pressure when the issue is happening. New/Good parts don't mean anything

If you use AFR error than the maths would be messed up how you have it setup. That is why I flagged it.

And timing at 5 degrees and even less can cause more problems. It isn't conservative. Its on the edge of/might be problematic

[tt460]

Thanks for the input. Updated the DTCs and tweaked the VE table and it's heading in the right direction. I'll run down the injector values to be sure they're correct before moving forward. Plan to replace the one WB02 that is flakey.